1. Field of the Invention
This invention relates to a motor having a commutator on which a ring varistor is mountable.
2. Related Background Art
The rotor of a motor provided with a commutator simply comprises a construction shown in FIG. 8 the accompanying drawings, i.e., an armature core 11 having a plurality of slots connected to the rotary shaft 6 of the rotor, a commutator 5 fixed coaxially with the rotary shaft 6 and comprising the same number of commutator pieces as the slots of the armature core 11, and a winding 10 for effecting connection between the commutator pieces and the slots of the armature core 11. FIGS. 4, 5 and 6 of the accompanying drawings show the vicinity of the commutator 5 of a motor having a commutator according to the prior art on an enlarged scale. The base portion of riser members 1 is fixed to the surface of the commutator 5 concentrically fixed to the rotary shaft 6 of the rotor of the motor. As a method of conducting a winding 4 to the riser members 1, there is fusing. This, as shown in FIG. 5, is a method of hooking the winding 4 on the end portion 2 of the riser members 1 which is not the base portions thereof, and thereafter bringing the riser members into close contact with each other at a position 3 and applying a high voltage thereto the thereby weld the close contact portion. Since a high voltage is used, the cover of the winding can be removed at the same time by the heat at this time and this is excellent in efficiency as compared with the step of removing the cover of the winding 4 by the used of soldering iron or the like.
FIG. 7 of the accompanying drawings shows the internal circuit of the motor. The commutator 5 comprises a plurality of commutator pieces 50, and the plurality of commutator pieces 50 are rotated to thereby effect the switching action, but during this switching, a counter-electromotive voltage is produced. This counter-electromotive voltage sometimes reaches several tens of thousands of volts, and in order to prevent an excessive electric current from flowing through the motor by this voltage, a ring varistor 7 is joined to the riser members 1 of the commutator 5. FIG. 6 shows the joined portions of the varistor 7 on an enlarged scale. As a method of joining the ring varistor 7, it has been practiced to effect fusing on the riser members, and thereafter insert the commutator and the riser members into the inner diameter portion of the ring varistor 7, fixing the ring varistor 7 in its floating state by a jig or the like, and join the ring varistor to the riser members 1 by soldering. In this structure, however, the riser members 1 and the ring varistor 7 are not in direct contact with each other, and conduction is effected through a soldered portion 8. Consequently, if malconduction is caused in the soldered portion 8, there has been the possibility of bad conduction occurring between the riser members 1 and the ring varistor 7. Accordingly, in order to prevent the influence of the counter-electromotive force and to have the motor not damaged, room for improvement is considered to be left in the method of joining the ring varistor to the riser member 1. Also, in the above-described conventional joining method, it is necessary to fix the not so large ring varistor 7 in its floating state, and this has not been good in working efficiency. Further, when the region of the ring varistor 7 which is to be soldered is predetermined, the circumferential positioning of the ring varistor 7 must be done accurately, and it has not been easy to effect this positioning on the ring varistor 7 in its floating state.
One aspect of this invention is to provide a riser member having a base portion fixed to the surface of the commutator of a rotor, a first turned-back portion bent so as to hook the winding of a motor, and a second turned-back portion provided on the side opposite to the base portion with respect to the first turned-back portion, to thereby enable a ring varistor to be supported by the second turned-back portion, and enable the mounting of the ring varistor to be effected easily. Further, when the ring varistor has been mounted, the second turned-back portion is in direct contact with the ring varistor and therefore, bad conduction attributable to soldering can be prevented.